The potato is the world's fourth most important food crop and by far the most important vegetable. Potatoes are currently grown commercially in nearly every state of the United States. Annual potato production exceeds 18 million tons in the United States and 300 million tons worldwide. The popularity of the potato derives mainly from its versatility and nutritional value. Potatoes can be used fresh, frozen or dried, or can be processed into flour, starch or alcohol. They contain complex carbohydrates and are rich in calcium, niacin and vitamin C.
The quality of potatoes in the food industry is affected by two critical factors: (1) potatoes contain large amounts of asparagine, a non-essential free amino acid that is rapidly oxidized to form acrylamide, a carcinogenic product, upon frying or baking; and (2) potatoes are highly susceptible to enzymatic browning and discoloration, an undesirable event which happens when polyphenol oxidase leaks out from the damaged plastids of bruised potatoes. In the cytoplasm, the enzyme oxidizes phenols, which then rapidly polymerize to produce dark pigments. Tubers contain large amounts of phosphorylated starch, some of which is degraded during storage to produce glucose and fructose. These reducing sugars react with amino acids to form Maillard products including acrylamide when heated at temperatures above 120° C. Two enzymes involved in starch phosphorylation are water dikinase R1 and phosphorylase-L (R1 and PhL). Browning is also triggered non-enzymatically as a consequence of the partial degradation of starch into glucose and fructose.
Many potato cultivars are susceptible to late blight, a devastating disease caused by the fungus-like oomycete pathogen Phytophthora infestans. Late blight of potato is identified by black/brown lesions on leaves and stems that may expand rapidly and become necrotic. Severe late blight epidemics occur when P. infestans grows and reproduces rapidly on the host crop.
Thus, there is a need to develop potato varieties with reduced levels of toxic compounds and increased resistance to disease, but without the use of unknown or foreign nucleic acids. The present disclosure satisfies this need.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification.